Magnetic head

ABSTRACT

Provided is a magnetic head including a bottom pole, a top pole spaced a predetermined distance apart from the bottom pole, an inductive write coil for forming a magnetic field at the bottom and top poles, and a magnetic shield layer positioned over the top pole.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a magnetic head forwriting/reading a magnetic signal on/from a recording medium, and moreparticularly, to a magnetic head constructed so as not to generatemagnetic concentration due to external magnetic field.

[0003] 2. Description of the Related Art

[0004] An apparatus for writing/reading a magnetic signal on/from arecording medium, e.g., a hard disk drive, includes a magnetic head forwriting and reading information. A magnetic head 10, as shown in FIG. 1,is installed in a slider 20 provided at one end of a swing arm 30, andmoves to a track being at a desired position on a recording medium (notshown) by rotation of the swing arm 30 to perform a write or readoperation.

[0005]FIG. 2 is an enlarged view of the magnetic head 10 shown in FIG. 1As shown in FIG. 2, the magnetic head 10 includes a magneto-resistivehead 14 for reading information and an inductive write head for writinginformation. The magneto-resistive head 14 reads a magnetic signalwritten on a recording medium, and the inductive write head including atop pole 11 and a bottom pole 12 for producing a leakage flux passingthrough the recording layer of the recording medium, and a write coil 13used as a current supply route, writes given information on a recordingmedium.

[0006] The inductive write head affects the quality of a signal writtenon a recording medium. That is, if inputting by the inductive write headis not clearly performed, reproduction cannot be satisfactorilyperformed even if the performance of the magneto-resistive head 14 isexcellent. In particular, the inductive write head is very sensitive toan external magnetic field. For example, if a magnetic stray fieldgenerated from a voice coil motor (VCM) for driving the swing arm isconcentrated by the inductive write head. This is called an antennaeffect, in which information is erroneously written on or erased from arecording medium by the external magnetic field concentrating in theinductive write head.

[0007]FIGS. 3A and 3B show the distribution of a magnetic flux inducedto an inductive write head and a recording medium by an antenna effectarising due to an external magnetic field.

[0008] As shown in FIGS. 3A and 3B, a magnetic field generated from anexternal magnetic field generating source 1 by an antenna effect extendstoward top and bottom poles 11 and 12 of an inductive write head. A softmagnetic layer 3 is formed under a recording layer 2 of a recordingmedium. In this case, magnetic concentration occurs at the top andbottom poles 11 and 12 of the inductive write head. In particular, asshown in FIG. 3B, in view of configuration of the top pole 11, a widthw′ of a portion positioned over the write coil 13 is much greater than awidth w of a portion facing the recording layer 2. For example, in thecase where the magnetic strength of a rear part of the top pole 11 is100 Oe (oersted), the magnetic strength of an edge part corresponding tothe recording layer 2 is 100×w′/w Oe. In other words, the magnetism atthe edge part is strengthened in a proportion of w′/w. As describedabove, the external magnetic field concentrated by the top and bottompoles 11 and 12 affects the recording layer 2 by being strengthened atthe edge part. In a vertical writing type magnetic head, erasure isfirst performed by a bottom pole and a write operation is then performedby a top pole. The external magnetic field is a stray field thatundesirably causes erasure of information and a write operation ofinformation. Major factors of the external magnetic field generatingsource 1 include a swing arm, which is a magnetic field generatingsource in an information recording apparatus and provides a magneticcircuit, and a VCM for driving the swing arm. The magnetic concentrationdue to the external magnetic field is disadvantageous for a high-densityinformation recording system.

SUMMARY OF THE INVENTION

[0009] To solve the above-described problems, it is an object of thepresent invention to provide a magnetic head which can effectivelysuppress a magnetic concentration due to an external magnetic field.

[0010] It is another object of the present invention to provide amagnetic head which can effectively write and erase erroneousinformation by suppressing concentration of an external magnetic field.

[0011] To accomplish the above objects, there is provided a magnetichead including a bottom pole, a top pole spaced a predetermined distanceapart from the bottom pole, an inductive write coil for forming amagnetic field at the bottom and top poles, and a magnetic shield layerwhich is positioned over the top pole and whose the leading edge isaligned with the leading edge of the top pole.

[0012] According to an embodiment of the present invention, the width ofthe magnetic shield layer is narrower than the width of the top pole.Also, an intermediate layer is preferably interposed between thetrailing edge of the magnetic shield layer and the trailing edge of thetop pole, and the intermediate layer is preferably made of a magneticmaterial. Further, a magneto-resistive head is positioned under thebottom pole.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above objects and advantages of the present invention willbecome more apparent by describing in detail preferred embodimentsthereof with reference to the attached drawings in which:

[0014]FIG. 1 is an extracted perspective view of a swing arm of aninformation recording apparatus, in which a general magnetic head isinstalled;

[0015]FIG. 2 is a schematic perspective view of a conventional magnetichead;

[0016]FIGS. 3A and 3B show the distribution of a magnetic fieldgenerated by the conventional magnetic head shown in FIG. 2, showingmagnetic concentration due to an external magnetic field;

[0017]FIG. 4 is a schematic front view of a magnetic head according tothe present invention;

[0018]FIG. 5A is an extracted side view of the magnetic head shown inFIG. 4, FIG. 5B is a plan view of the magnetic head shown in FIG. 4, andFIG. 5C is an extracted perspective view of the magnetic head shown inFIG. 4; and

[0019]FIG. 6A and 6B show the distribution of a magnetic field generatedby the magnetic head according to the present invention, showing thedistribution of a magnetic field due to an external magnetic field.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring to FIG. 4, a multi-layer stack structure for writingand reading information is formed on a substrate 101. A magnetic shieldlayer 150, which features the present invention, is formed on thetopmost layer of the multi-layer stack structure. A top pole 110 isformed under and spaced a predetermined distance apart from the magneticshield layer 150, and a bottom pole 120 is formed under the top pole110. A magneto-resistive head 140 is positioned under the bottom pole120. The magnetic shield layer 150 is formed of a metal, preferably amagnetic material, and has a width greater than that of the top pole 110or the bottom pole 120.

[0021] Here, the widths of upper and lower parts of the magnetic shieldlayer 150 are preferably equal to each other. In the case where thewidths of upper and lower parts of the magnetic shield layer 150 aredifferent, they must be adjusted such that the magnetic strengthconcentrated in the edge part is less than that required for erasure ora write operation performed on a recording layer. A lower-partstructure, excluding the magnetic shield layer 150 from theaforementioned multi-layer stack structure, is the same as the structureof the conventional magnetic head. All parts of a magnetic head are notshown and described in the drawing.

[0022] Referring to FIG. 5A, in a magnetic head 100, a top pole 110 isformed on a bottom pole 120. An inductive write coil 130 for writinginformation is positioned between the bottom pole 120 and the top pole110. The bottom pole 120 and the top pole 110 are spaced a predetermineddistance apart from a recording layer of a recording medium. A magneticshield layer 150 is formed above and spaced a predetermined distanceapart from the top pole 110. An edge 151 of the magnetic shield layer150 is aligned with leading edges 111 and 121 of the bottom and toppoles 120 and 110. A trailing edge 122 of the bottom pole 120 and atrailing edge 152 of the top pole 110 extend by the same length. Anintermediate layer 160 is interposed between these edges 122 and 152.

[0023]FIG. 5C is an extracted view of the top pole 110, showing thestate in which a magnetic flux is formed. Assuming that across-sectional area of the leading edge 111 of the top pole 110 is A₂,and a cross-sectional area of the trailing edge 1 12 is A₁,A₁×B₁,=A₂×B₂, where B₁ denotes a magnetic flux density at the trailingedge 112 of the top pole 110 and B₂ denotes a magnetic flux density atthe leading edge 111 of the top pole 110. In other words, the number ofmagnetic fluxes passing through the top pole 110 equals at the leadingand trailing edges 111 and 112. Thus, the magnetic flux density B₂ atthe leading edge 111 of the top pole 110 is inversely proportional tothe cross-sectional area A₂ thereat, as B₂=(A₁/ A₂)·B₁. According toexperimentation, in order to obtain a magnetic flux density in whichinformation can be more effectively written, the cross-sectional area A₂at the leading edge 111 of the top pole 110 is greater than or equal toa fifth (⅕) the cross-sectional area A₁ at the trailing edge 112 of thetop pole 110, preferably ⅕.

[0024] The above-described magnetic head positioned at an edge of aswing arm of an information recording apparatus is fixed to a front faceof a slider flying over the recording plane of a recording medium by anaerial negative pressure. The intermediate layer 160 may be formed of anon-magnetic material. However, in order to suppress magneticconcentration due to an external magnetic field, a magnetic material ismore preferably used as the intermediate layer 160. The magnetic headhaving a multi-layer stack structure optionally includes theintermediate layer 160, and the intermediate layer 160 may not beformed. However, the magnetic head essentially includes a recordinglayer where a write operation actually occurs, and a soft magnetic layerprovided under the recording layer.

[0025]FIGS. 6A and 6B show a magnetic circuit provided when an externalmagnetic field is produced at the magnetic head having theaforementioned configuration.

[0026] As shown in FIGS. 6A and 6B, a magnetic field generated from theexternal magnetic field generating source 1 by an antenna effect extendstoward the top and bottom poles 110 and 120. Here, a magnetic circuit isproduced by the magnetic shield layer 150 formed over the top pole 110.In other words, in the case where the intermediate layer 160 providedbetween the magnetic shield layer 150 and the trailing edge of thebottom pole 120 is formed of a magnetic material, a magnetic field isproduced from the external magnetic field generating source 1 withrespect to the intermediate layer 160. In this case, the intermediatelayer 160 provides a magnetic circuit, which branches off the magneticfield into the magnetic shield layer 150 and the bottom pole 120 withoutconcentrating the induced magnetic field.

[0027] Thus, the magnetic field generated from the external magneticfield generating source 1 is distributed to the magnetic shield layer150, the top pole 110 and the bottom pole 120, thereby suppressingmagnetic concentration at the recording layer 2. Here, the strength ofthe magnetic field passing through the top pole 110 position between thebottom pole 120 and the magnetic shield layer 150 is weaker than that ofthe magnetic field passing between the bottom pole 120 and the magneticshield layer 150. The weakened magnetic field concentration makes amagnetic field smaller than is required for writing or erasinginformation, thereby preventing information from erroneously beingwritten or erased due to an external magnetic field. In particular, thewidth of the magnetic shield layer 150 is wider than that of the toppole 110 or the top pole 120, so that an external magnetic field can beshielded or absorbed to then be distributed to the entire area of themagnetic shield layer 150.

[0028] As described above, the external magnetic field is mainlygenerated from a swing arm, which is a magnetic field generating sourcein an information recording apparatus and provides a magnetic circuit,and a VCM for driving the swing arm. However, the magnetic shield layer150 according to the present invention suppresses magnetic concentrationwith respect to the top and bottom poles 110 and 120 provided under themagnetic shield layer 150 due to the external magnetic field.

[0029] The magnetic head according to the present invention isconstructed to effectively distribute and shield an external magneticfield, thereby reducing an antenna effect and exhibiting excellentrecording characteristics.

[0030] While this invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A magnetic head comprising: a bottom pole; a top pole spaced a predetermined distance apart from the bottom pole; an inductive write coil for forming a magnetic field at the bottom and top poles; and a magnetic shield layer positioned over the top pole.
 2. The magnetic head of claim 1, wherein the width of the magnetic shield layer is narrower than the width of the top pole.
 3. The magnetic head of claim 1 or 2, wherein the leading edge of the magnetic shield layer is aligned with the leading edge of the top pole.
 4. The magnetic head of claim 3, wherein an intermediate layer is interposed between the trailing edge of the magnetic shield layer and the trailing edge of the top pole.
 5. The magnetic head of claim 4, wherein the intermediate layer is made of a magnetic material.
 6. The magnetic head of claim 1 or 2, wherein an intermediate layer is interposed between the trailing edge of the magnetic shield layer and the trailing edge of the bottom pole.
 7. The magnetic head of claim 6, wherein the intermediate layer is made of a magnetic material.
 8. The magnetic head of claim 1, wherein the magnetic shield layer is made of a magnetic material.
 9. The magnetic head of claim 1, wherein the cross-sectional area of the leading edge of the top pole is greater than or equal to a fifth (⅕) that of the trailing edge of the top pole. 